Hitherto it has been known to use mobile concrete mixing trucks to mix concrete and to deliver that concrete to a site where the concrete may be required. Generally, the particulate concrete ingredients are loaded at a central depot. A certain amount of liquid component may be added at the central depot. Generally the majority of the liquid component is added at the central depot, but the amount of liquid is often adjusted. The adjustment is often unscientific—the driver add water from any available water supply (sometimes there is water on the truck) by feeding a hose directly into the mixing barrel and guessing as to the water required. Operators attempt to tell by experience the correct or approximate volume of water to be added according to the volume of the particulate concrete ingredients. The adding of the correct amount of liquid component is therefore usually not precise.
It is known, that if concrete is mixed with excess liquid component, the resulting concrete mix does not dry with the required structural strength. At the same time, concrete workers tend to prefer more water, since it makes concrete easier to work. Accordingly, slump tests have been devised so that a sample of the concrete mix can be tested with a slump test prior to actual usage on site. Thus, if a concrete mixing truck should deliver a concrete mix to a site, and the mix fails a slump test because it does not have sufficient liquid component, extra liquid component may be added into the mixing barrel of the concrete mixing truck to produce a required slump in a test sample prior to actual delivery of the full contents of the mixing barrel. However, if excess water is added, causing the mix to fail the slump test, the problem is more difficult to solve, because it is then necessary for the concrete mixing truck to return to the depot in order to add extra particulate concrete ingredients to correct the problem. If the extra particulate ingredients are not added within a relatively short time period after excessive liquid component has been added, then the mix will still not dry with the required strength.
In addition, if excess liquid component has been added, the customer cannot be charged an extra amount for return of the concrete mixing track to the central depot for adding additional particulate concrete ingredients to correct the problem. This, in turn, means that the concrete supply company is not producing concrete economically.
One method and apparatus for mixing concrete in a concrete mixing device to a specified slump is disclosed in U.S. Pat. No. 5,713,663 (the '663 patent), the disclosure of which is hereby incorporated herein by reference. This method and apparatus recognizes that the actual driving force to rotate a mixing barrel filled with particulate concrete ingredients and a liquid component is directly related to the volume of the liquid component added. In other words, the slump of the mix in the barrel at that time is related to the driving force required to rotate the mixing barrel. Thus, the method and apparatus monitors the torque loading on the driving means used to rotate the mixing barrel so that the mix may be optimized by adding a sufficient volume of liquid component in attempt to approach a predetermined minimum torque loading related to the amount of the particulate ingredients in the mixing barrel.
More specifically, sensors are used to determine the torque loading. The magnitude of the torque sensed may then be monitored and the results stored in a storage means. The store means can subsequently be accessed to retrieve information therefrom which can be used, in turn, to provide processing of information relating to the mix. In one case, it may be used to provide a report concerning the mixing.
Improvements related to sensing and determining slump are desirable.
Other methods and systems for remotely monitoring sensor data in delivery vehicles are disclosed in U.S. Pat. No. 6,484,079 (the '079 patent), the disclosure of which is also hereby incorporated herein by reference. These systems and methods remotely monitor and report sensor data associated with a delivery vehicle. More specifically, the data is collected and recorded at the delivery vehicle thus minimizing the bandwidth and transmission costs associated with transmitting data back to a dispatch center. The '079 patent enables the dispatch center to maintain a current record of the status of the delivery by monitoring the delivery data at the delivery vehicle to determine whether a transmission event has occurred. The transmission event provides a robust means enabling the dispatch center to define events that mark the delivery progress. When a transmission event occurs, the sensor data and certain event data associated with the transmission event may be transmitted to the dispatch center. This enables the dispatch center to monitor the progress and the status of the delivery without being overwhelmed by unnecessary information. The '079 patent also enables data concerning the delivery vehicle and the materials being transported to be automatically monitored and recorded such that an accurate record is maintained for all activity that occurs during transport and delivery.
The '079 patent remotely gathers sensor data from delivery vehicles at a dispatch center using a highly dedicated communications device mounted on the vehicle. Such a communications device is not compatible with status systems used in the concrete industry.
Improvements related to monitoring sensor data in delivery vehicles using industry standard status systems are desirable.
A further difficulty has arisen with the operation of concrete delivery vehicles in cold weather conditions. Typically a concrete delivery truck carries a water supply for maintaining the proper concrete slump during the delivery cycle. Unfortunately this water supply is susceptible to freezing in cold weather, and/or the water lines of the concrete truck are susceptible to freezing. The truck operator's duties should include monitoring the weather and ensuring that water supplies do not freeze; however, this is often not done and concrete trucks are damaged by frozen pipes, and/or are taken out of service to be thawed after freezing.
Accordingly, improvements are needed in cold weather management of concrete delivery vehicles.